Search

Graphene-based inorganic layered materials have developed as a versatile, new class of nanomaterials and drawn huge scientific interest, owing to its thickness-dependent physical properties, exfoliated two-dimensional crystals in various technological and industrial applications. This work is the first demonstration of the fabrication of low dimensional bismuth selenide (Bi2Se3) NPs functionalized reduced graphene oxide (rGO) on the platinum electrode (Pt-E) for the ultra-sensitive and simultaneous detection of acetaminophen (ACT) and L-DOPA (LD) in the presence of ascorbic acid (AA) in various biological samples and pharmaceuticals. The constructed electrode accelerates the electron transfer reactions of LD and ACT without interfering with the electron transfer reactions of AA, which was an electroactive coexisting chemical. At pH 6.0 in 0.1 M phosphate buffer solution, Bi2Se3 NPs/rGO/Pt-E showed a sixfold and fivefold increase in cyclic voltammetry for LD and ACT signals, respectively, when compared to bare Pt-E. Under the optimal conditions, differential pulse voltammetry (DPV) demonstrated that the anodic peak currents were linearly dependent on the concentrations of LD (0.006–0.25 mM) and ACT (0.0045–0.14 mM) at anodic peak potentials of + 0.25 and + 0.52 V, respectively. With a signal to noise (S/N) ratio of 3, acceptable detection limits of 0.23 and 0.17 M were achieved for both LD and ACT, with strong intra- and inter-electrode repeatability. Overall, the fabricated nanosensor offered numerous advantages including ease to fabricate, ultra-sensitivity, good stability, and reproducibility towards the detection of LD and ACT in various bioloical samples and pharmaceuticals. The amounts of LD and ACT were also identified in commercial pharmaceuticals and synthetic urine samples to validate the applicability of the modified electrode.

Monitoring of high intensity artificial sweeteners in the food industry for environmental and human health has become relevant in recent years. This work exploits the electrocatalytic properties of the laccase enzyme for sensing of a high intensity sweetener sucralose experimentally and supported by computational modeling. The fabrication of the laccase biosensor was achieved using laccase immobilized onto zinc oxide nanoparticles (ZnONPs) capped with p-amino thiophenol (ATP) and covalently attached to graphene oxide (GO) modified glassy carbon electrode (Lac/ZnONPs-ATP-GO/GCE). The developed biosensor exhibited an 8-fold enhancement of differential pulse voltammetry signals compared with the bare GCE at pH 5.0 in a 0.1 M phosphate buffer. The amplification of signals was due to a firm binding of laccase onto the surface of GO through high isoelectric point ZnONPs, exhibiting an enzymatic catalytic activity towards the oxidation of sucralose (SUC) at + 0.25 V (vs. Ag/AgCl). Under the optimized experimental conditions, the anodic peak current linearly increased with the sucralose concentrations ranging from 0.025–0.1 mM (R2 = 0.9984) and 0.25–1.0 mM (R2 = 0.9979) with a detection limit (S/N = 3) of 0.32 μM. Furthermore, the proposed strategy was confirmed by assessing the interactions between the sucralose and the laccase using computational tools. First, the density functional theory (DFT) calculations of SUC revealed a HOMO–LUMO energy gap of − 0.2555 eV, suggesting a great tendency to act as an electron donor. Furthermore, adsorption and sucralose-laccase docking studies were carried out to better understand the redox mechanisms. These results revealed that SUC forms hydrogen bonds with ILE 230 and GLN 228 and other amino acids of the hydrophobic channel of the binding sites, thereby facilitating the redox reaction for the detection of sucralose.

The analysis of β-blockers in pharmaceutical, biological and environmental samples has gained much interest due to their wide applications. The aim of this study was to develop an enzyme-based biosensor using hexagonal-shaped low-dimensional Bi

The inactivation of bacteria and the degradation of organic pollutants by engineered nanomaterials (NMs) are very effective approaches for producing safe and clean drinking water. The development of new NMs which can act as NIR light mediated antimicrobial agents as well as photocatalytic agents is highly desired. In this study, a novel Bi2Se3 nanoplates (NPs) NM was prepared by a high-temperature reaction (colloidal synthesis) followed by wrapping of the surface with polyethyleneimine (PEI) through electrostatic interactions. The developed Bi2Se3 NPs/PEI exhibited excellent NIR light activated antimicrobial properties for bacterial eradication and efficient photocatalytic properties for organic dye degradation. The results showed that upon 808 nm laser irradiation the engineered Bi2Se3 NPs/PEI eradicated ∼99% of S. aureus and ∼97% of E. coli bacteria within 10 minutes of irradiation through combined dual-modal photothermal therapy (PTT) and photodynamic therapy (PDT) via the generation of heat and reactive oxygen species, respectively. The contributions of PTT and PDT were found to be in a ratio of nearly 4 : 1 in the killing of both species of bacteria. In addition, Bi2Se3 NPs/PEI also acted as an excellent photocatalyst under illumination by a halogen lamp equipped with a 700–1100 nm band pass filter to achieve degradation efficiencies of ∼95% for methylene blue and ∼93% for Rhodamine B within 3 and 4 h, respectively. To the best of our knowledge, this is the first demonstration of these NIR light activated antimicrobial properties, photodynamic properties and photocatalytic properties mediated by Bi2Se3 NPs.

The metal complexes can demonstrate various interesting biological activities in the human body. However, the role of certain metal ions for specific cell activities is still subject to debate. This study is aimed at comparing the thermochemical properties of neotame (artificial sweetener) and α, β-fructose in gas phase and water medium. The interaction of α and β-fructose, neotame with monovalent and divalent metal ions was studied and comprehended by density functional theory (DFT) using B3LYP functional, 6–311 + G (d, p) and D3 basis set. Metal ion affinities (MIA) values depicted that ionic radius of metal ions played an important role in the interaction of α, β-fructose and neotame. The ∆G parameter was calculated to predict and understand the interaction of metal ions with α and β-fructose, neotame. The results suggested that the presence of hydroxyl groups and oxygen atoms in sugar molecules acted as preferred sites for the binding and interaction of mono and divalent ions. For the first time computational study has been introduced in the present study to review the progress in the application of metal binding with sugar molecules especially with neotame. Moreover, voltammetric behaviour of neotame-Zn2+ was studied using cyclic and differential pulse voltammetry. The obtained results suggest that the peak at −1.13 V is due to the reduction of Zn2+ in 0.1 M phosphate buffer medium at pH 5.5. Whereas, addition of 6-fold higher concentration of neotame to the ZnCl2.2H2O resulted in a new irreversible cathodic peak at −0.83, due to the reduction of neotame-Zn2+ complex. The Fourier transform infrared spectroscopy (FTIR) results indicates that the β-amino group (-NH) and carboxyl carbonyl (-C = O) groups of neotame is participating in the chelation process, which is further supported by DFT studies. The findings of this study identify the efficient chelation factors as major contributors into metal ion affinities, with promising possibilities to determine important biological processes in cell wall and glucose transmembrane transport.

A highly sensitive and novel electrochemical sensor for the detection of neotame using differential pulse voltammetry with a modified glassy carbon electrode is presented. The method was further customized by the fabrication of the electrode surface with copper nanoparticles-ammonium piperidine dithiocarbamate-mutiwalled carbon nanotubes assimilated with β-cyclodextrin. The multiwalled carbon nanotubes assimilated with β-cyclodextrin/glassy carbon electrode exhibited catalytic activity towards the oxidation of neotame at a potential of 1.3 V at pH 3.0. The transmission electron microscopy, thermogravimetric analysis, frontier transform infrared spectroscopy and cyclic voltammetry were employed to characterize the electrochemical sensor. The sensitivity and detection limits of the electrode increased two-fold in contrast to the β-CD-MWCNTs/GCE sensor. The developed method was successfully applied for the determination of neotame in food samples, with results similar to those achieved by our modified capillary electrophoresis method with a 96% confidence level.

An electrokinetic chromatographic method was developed for the chiral separation of neotame, a new high intensity artificial sweetener, using a chiral separating agent heptakis 2,3,6-tri-o-methylbetacyclodextrin. The purpose of this study was to better understand diastereomer-resolution interactions between neotame and the chiral separating agent. Molecular docking studies were performed to elucidate the mechanism of the separation. The optimum conditions were 50 mM phosphate buffer, pH 5.5, applied voltage 20 kV, cassette temperature of 30°C, and a 4 s sample injection time. The calibration curve showed good linearity (r2 > 0.99) with recoveries for both diastereomers, ranging from 95.66–99.00% and the limits of detection for L,L-neotame and D,D-neotame were 0.01857 and 0.08214 mM, respectively. The developed method showed analytical precision with relative standard deviations (n = 5) of 1.20% and 1.17% with respect to migration time and peak area, respectively. A large difference in the interaction ener...